.....Some impotant MCQ on Transmission Distribution of Power......
TDP MCQ
Exam question paper
Subject: Transmission Distribution of Power
Model paper 02. Number of questions-70
www.nibeditapolytechnic.com
Answer all the questions
1. 3-phase, 4-wire system is commonly used for
a. Primary distribution
b. Secondary distribution
c.Primary transmission.
d. Secondary transmission.
Ans:Secondary distribution
2. The rated Voltage of a three phase power system is given by
a. RMS phase voltage
b. Peak phase voltage.
c. RMS line to line voltage
d. Peak line to line voltage
Ans- RMS line to line voltage.
3. In a transmission system the feeder supplies power to
a. transformer substations
b.service means
c. distributors
Ans:Distributors
4. Feeder is designed mainly from the point of view of
a. its current carrying capacity
b. voltage drop in it
c. operating voltag
d.operating frequency
Ans: a
5. By increasing the transmission voltage double of its original value, the same power can be dispatched keeping the line loss
a. equal to its original value
b.half of original value
c.double the original value
d. one fourth of original value.
Ans : d
6. If a fixed amount of power is to be transmitted over certain length with fixed power loss,it can be said that volume of conductor is
a.inversely proportional to magnitude of the voltage and that of power factor of the load b.inversely proportional to square of the voltage and Square of power factor of the load .
c. proportional to square of voltage and that of power factor of the Lord
Ans: b.
7. In a transmission system the weight of copper used is proportional to
a. E2. b.E. c.1/E2. d.1/E
Ans: c
8.Improving power factor
a. Reduces current for a given output integers losses in line increases the cost of station equipment
Ans: a
9. For the same conductor length, same amount of power, same losses and maximum voltage to earth, which system requires minimum conductor area
a. Single phase AC
b. Three phase AC
c. 2 wire AC
d. 3 wire DC
Ans: d
10. Which of the following distribution system is preferred for good efficiency and higher economy
a. Single phase, two wire system
b 2-Phase , 3- wire system
c. 3- phase 3- wire system
d. 3 -phase 4- wire system
Ans: d
11.The main reason for using high voltage for long distance power transmission is
a.Reduction in transmission losses
b.Reduction in time of transmission
c. increases in system reliability
Ans: a
12. The highest transmission voltage used in India is
a.400kv b.220Kv. c.132 KV d.765 KV
Ans: d.
13.If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wested in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as
a.Lenz's law b.Kelvin's law c. Faraday's law d. Ohm's law
Ans: b
14.For high voltage transmission lines conductors are suspended from towers so as to a.Increase clearance from ground .
b. Reduce clearance from ground .
c. Take care of increase in length.
d. reduce wind and snow effects
Ans: a
15. The wooden poles well impregnated with creosite oil or any preservative compound have life of
a. 25 - 30 years b. 20- 25years c. 10- 15 years d. 5 - 10 years
Ans: a
16. Steel poles for transmission lines need protection against
a. Borer. b.Terminates c. corrosion
Ans: c
17. RCC poles usually have the spans of
a. 250 to 400 m. b. 80 to 150 m. c. 50 to 80 d. 25 to 50 m
Ans: b
18. In India for distribution of electric power we usually use
a . Wooden poles b. Steel poles c. RCC poles d. both B and C
Ans: d
19. Which of the following properties has got higher value for aluminium in comparison to that of copper
a. Electrical resistivity b.Melting point c.Thermal conductivity d. Specific gravity
Ans: a
20. In a 7/30 ACSR conductor why is grease put between steel and aluminium conductors?
a. To reduce corrosion by electrolytic action between zinc and aluminium
b. To reduce friction between the strands
c. To reduce leakage of current from aluminium strands to steel strands
d. To eliminate air pockets
Ans: a
21.ACSR is used in place of copper in overhead lines because of
a. Higher current carrying capacity b. being lighter in weight. c. economy. d.higher tensile strength
Ans: c
22. The material used for the manufacture of ground wire is
a. aluminium. b. galvanized steel. c. cast iron. d. Stainless steel
Ans: b
23.Guy wire is employed for
a. Providing protection against surges. b.Providing emergency route. c. Supporting the poles
Ans: c
24. Effect of temperature rise in overhead lines is to
a. Increase in sag and decrease the tension
b.Decrease the sag and increase the tension. c. increase both. d.decrease both.
Ans: a
25. Which of the following statements is correct
a. Ice on conductors increases Skin effect.
b.Wind pressure reduces corona effect.
c.Wind pressure is taken to act at perpendicular to that for ice.
d.Ice on conductor reduces sag .
Ans: c.
26.Wind loading in coastal regions it in the range of
a. 40 to 50 kg per meter square .
b. 150 kg per metre square. c. 96 kg per metre square
Ans: b
27.The maximum tension in a section of overhead line conductor between two supports of unequal height occurs at
a. The highest support.
b. The lower point .
c.In the the midpoint of the conductor.
Ans : a
28. Stringing chart is useful
a. For finding the sag in the conductor.
b.In the design of tower.
c.In the design of insulator string.
d.Finding the distance between towers.
Ans: a
29.Hot template curves are plots of
a. temperature and humidity.
b. conductor sag and span length .
c.conductor weight and sag.
Ans: b
30. The effect of wind pressure is more predominant on
a. insulator.
b.transmission lines.
c.supporting towers.
Ans: c
31.Galloping in transmission line conductors arises due to
a. Asymmetrical layer of ice formation.
b. Vortex phenomenon in light winds.
C.Heavy weight of the line conductors.
d. Adoption of horizontal conductors configuration.
Ans:a
32. The sag of the conductors of a transmission line is 2.5 metre when the Span is 250 metre .Now if the height of supporting tower is increased by 25% , the sag will
a. Reduced by 25% .
b. Increased by 95% .
c.Reduced by 12.5% .
d.Remain unchanged.
Ans: d
33.Stranded conductors usually have a central wire around which there are successive layers of 6 ,12, 18 ,24 wires.For n layers ,the total number of individual wires is
a.3n(n+1) b. 2n(n+1) c.3n(n+1)+1 d.2n(n+1) +1
Ans: c
34.The diameter of each strand is d then the diameter of n layer stranded conductor will be
a. (2n+1)d. b. 3(n+1)d. c.(2n-1)d. d.3(n-1)d
Ans: a
35.Strain type insulators are used
a. At dead end
b. At intermideate anchor towers
c.On straight runs
d. a. and b.
Ans:d
36.Wavy structure of pin insulators increases its
a. Mechanical strength.
b. Puncture strength.
c.Flash over strength.
d. Thermal strength.
Ans:c
37.The voltage rating of a multiple shell pin type insulator unit cannot be increased beyond a limiting value by increasing the number of shells because,
a. The internal voltage distribution between shells becomes unequal.
b. The leakage path resistance starts diminishing .
c.The disruptive critical voltage for the material of the insulator is reached.
d. The puncture voltage of the material of the insulator is reached.
Ans:a
38. Post type insulators are generally used in lines operating
a.Avobe 100kv. b. below 33kv. c. at any voltage level ht or eht
Ans: c
39.In a string of insulators for 400 KV AC overhead transmission line lies in the range of
a. 32 to 33. b. 22 to 23 . c. 15 to 16 . d. 9 to 10
Ans:b.
Note:
2-3------33kv
5-6------66Kv
9-10-----132Kv
15-16------220kv
40. The non uniform distribution of voltage across the units in a string of suspension type insulator is due to
a . Unequal self capacitance of the units .
b.non-uniform distance of separation of the units from the tower body.
c. the existence of stray capacitance between the metallic junctions of the units and the tour body
d. non uniform distance between the cross arms and the units
Ans: c
41. The string efficiency of a string of suspension insulators is dependent on
a. size of the insulators. b. number of disc in the string. c. size of Tower
Ans: bb.
42. If the frequency of transmission system is changed from 50 Hz to 100 Hz,the string efficiency .
a. will increases. b. will decreases .
c. remain unchanged .
d. parameters may increases or decreases depending on the line parameters
Ans: c
43. The string efficiency of a High Voltage line is around
a. Hundred percent B. the 80%. c. 40. d.10%
44. The ratio of puncture voltage to the flash over voltage of a line insulator is
a. equal to 1
b.lower than one.
C.much greater than 1
Ans: c
45. The insulators may fail due to
a.flash over. b.short circuit.Deposition of dust. d. any of the avobe
Ans: d
46. The purpose of Guard ring in transmission lines is to
a.reduce the earth capacitance of the lowest unit
b. increased the earth capacitance of the lowest unit
c. reduce the transmission line losses d.increase the voltage distribution across the disc
Ans: a
47. Corona is
a. partial breakdown of Air .
b.complete breakdown of air
c. sparking between lines.
d.increase of resistance in line
Ans: b
48.Which of the following statements is true regarding Corona
a. Corona takes place at a voltage lower than breakdown voltage
b. takes place at a voltage higher than breakdown voltage.
c. Corona is a current phenomenon.
d. Corona increases the transmission line efficiency.
Ans: a
49.Ozone effect can be detected by
a.presence of ozone detected by odour.
b. hissing sound. c. faint luminous glow of bluish colour. d. all of the above
Ans: d
50. Corona loss increases with
a.decrease in conductor size and increase in supply frequency
b. increased in both conductor size and supply frequency
c. decrease in both conductor size and supply frequency
d. increase in conductor size and decrease in supply frequency
Ans: a
See the loss fomula of corona.
51.The good effect of Corona on overhead lines is to
a. increase the line carrying capacity due to conducting ionized air envelope around the conductor
b. Increase the power factor due to Corona loss.
c. reduces the radio interference from the conductor
d. Reduce the steepness of surge fronts.
Ans : d
52.Corona loss can be reduced by the use of hollow conductor because
a. the current density is reduced
b. the Eddy current in the conductor is eliminated.
c. for a given cross-section, the radius of the conductor is increased.
d. of better ventilation in the conductor
Ans: c
53. Bundled conductors reduce
a.surface electric stress of conductor
b. increases the line reactance.
c. decreases the line capacitance
Ans: a
54.The charging current transmission line increases due to corona effect because Corona increases
a.line current. b. effective line voltage. c.power loss in lines. d. the effective conductor diameter
Ans: d
55. The only advantage of Corona is that it
a. produces a pulsating Luminous glow.
b. makes line current sinusoidal.
c. works as a safety valve for surgesd.
d. the ozone gas is produced
Ans: c
56.What is the approximate breakdown strength of atmospheric air at N.T.P?
a. 0.3kv/cm b. 1.0 kv/cm. c. 3kv/cm. d. 30kv/cm
Ans: d
57.Skin effect in transmission line is due to a.supply frequency b. self inductance of conductor. c. high sensitivity of material in the centre. D both a. And b
Ans: d
58: when an alternating current flows through a conductor
a. Entire current passes through the core of the conductor
b. portion of conductor near the surface carries more current in comparison to the core.
C.current remains uniformly distributed over the cross section of the conductor
d. portion of conductor near the surface carries lesscurrent in comparison to the Core.
Ans: b
59. Iincreasing the frequency of transmission line will
a. increase shunt reactance. b. decrease line resistance. c. increase line resistance. d. decrease series resistance
Ans: c
60.Skin effect exist in
a. cable carrying DC current.
b.d c transmission line only. c. a c transmission line only. d. DC as well as AC transmission line.
Ans: c
True false question
61. single phase AC power pulsates around the average value at the supply frequency. Ans: False
62. the best method is to employ DC system for generation and distribution and ac system for transmission. Ans: False
63. Overhead system is more safer than underground system. Ans: False
64. The voltage drop in underground system is very low as compared to to that in overhead system. Ans: True
65. With the increase in voltage of transmission the insulation needed between the conductors and earthed tower increases. Ans: True
66. Economical cross section of conductor can be determined by Ferranti effect. Ans: False
67. Guy wire generally make an angle of 45 degree to 60 degree with the surface of the earth. Ans: True.
68. Increase in temperature in overhead transmission line causes decrease in stress but increase in length. Ans: True
69. Sag is directly proportional to the square of the span. Ans: True
70.Top most conductor in HV transmission line is earth conductor. Ans: True
..............
palashganga@gmail.com
TDP MCQ
Exam question paper
Subject: Transmission Distribution of Power
Model paper 02. Number of questions-70
www.nibeditapolytechnic.com
Answer all the questions
1. 3-phase, 4-wire system is commonly used for
a. Primary distribution
b. Secondary distribution
c.Primary transmission.
d. Secondary transmission.
Ans:Secondary distribution
2. The rated Voltage of a three phase power system is given by
a. RMS phase voltage
b. Peak phase voltage.
c. RMS line to line voltage
d. Peak line to line voltage
Ans- RMS line to line voltage.
3. In a transmission system the feeder supplies power to
a. transformer substations
b.service means
c. distributors
Ans:Distributors
4. Feeder is designed mainly from the point of view of
a. its current carrying capacity
b. voltage drop in it
c. operating voltag
d.operating frequency
Ans: a
5. By increasing the transmission voltage double of its original value, the same power can be dispatched keeping the line loss
a. equal to its original value
b.half of original value
c.double the original value
d. one fourth of original value.
Ans : d
6. If a fixed amount of power is to be transmitted over certain length with fixed power loss,it can be said that volume of conductor is
a.inversely proportional to magnitude of the voltage and that of power factor of the load b.inversely proportional to square of the voltage and Square of power factor of the load .
c. proportional to square of voltage and that of power factor of the Lord
Ans: b.
7. In a transmission system the weight of copper used is proportional to
a. E2. b.E. c.1/E2. d.1/E
Ans: c
8.Improving power factor
a. Reduces current for a given output integers losses in line increases the cost of station equipment
Ans: a
9. For the same conductor length, same amount of power, same losses and maximum voltage to earth, which system requires minimum conductor area
a. Single phase AC
b. Three phase AC
c. 2 wire AC
d. 3 wire DC
Ans: d
10. Which of the following distribution system is preferred for good efficiency and higher economy
a. Single phase, two wire system
b 2-Phase , 3- wire system
c. 3- phase 3- wire system
d. 3 -phase 4- wire system
Ans: d
11.The main reason for using high voltage for long distance power transmission is
a.Reduction in transmission losses
b.Reduction in time of transmission
c. increases in system reliability
Ans: a
12. The highest transmission voltage used in India is
a.400kv b.220Kv. c.132 KV d.765 KV
Ans: d.
13.If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wested in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as
a.Lenz's law b.Kelvin's law c. Faraday's law d. Ohm's law
Ans: b
14.For high voltage transmission lines conductors are suspended from towers so as to a.Increase clearance from ground .
b. Reduce clearance from ground .
c. Take care of increase in length.
d. reduce wind and snow effects
Ans: a
15. The wooden poles well impregnated with creosite oil or any preservative compound have life of
a. 25 - 30 years b. 20- 25years c. 10- 15 years d. 5 - 10 years
Ans: a
16. Steel poles for transmission lines need protection against
a. Borer. b.Terminates c. corrosion
Ans: c
17. RCC poles usually have the spans of
a. 250 to 400 m. b. 80 to 150 m. c. 50 to 80 d. 25 to 50 m
Ans: b
18. In India for distribution of electric power we usually use
a . Wooden poles b. Steel poles c. RCC poles d. both B and C
Ans: d
19. Which of the following properties has got higher value for aluminium in comparison to that of copper
a. Electrical resistivity b.Melting point c.Thermal conductivity d. Specific gravity
Ans: a
20. In a 7/30 ACSR conductor why is grease put between steel and aluminium conductors?
a. To reduce corrosion by electrolytic action between zinc and aluminium
b. To reduce friction between the strands
c. To reduce leakage of current from aluminium strands to steel strands
d. To eliminate air pockets
Ans: a
21.ACSR is used in place of copper in overhead lines because of
a. Higher current carrying capacity b. being lighter in weight. c. economy. d.higher tensile strength
Ans: c
22. The material used for the manufacture of ground wire is
a. aluminium. b. galvanized steel. c. cast iron. d. Stainless steel
Ans: b
23.Guy wire is employed for
a. Providing protection against surges. b.Providing emergency route. c. Supporting the poles
Ans: c
24. Effect of temperature rise in overhead lines is to
a. Increase in sag and decrease the tension
b.Decrease the sag and increase the tension. c. increase both. d.decrease both.
Ans: a
25. Which of the following statements is correct
a. Ice on conductors increases Skin effect.
b.Wind pressure reduces corona effect.
c.Wind pressure is taken to act at perpendicular to that for ice.
d.Ice on conductor reduces sag .
Ans: c.
26.Wind loading in coastal regions it in the range of
a. 40 to 50 kg per meter square .
b. 150 kg per metre square. c. 96 kg per metre square
Ans: b
27.The maximum tension in a section of overhead line conductor between two supports of unequal height occurs at
a. The highest support.
b. The lower point .
c.In the the midpoint of the conductor.
Ans : a
28. Stringing chart is useful
a. For finding the sag in the conductor.
b.In the design of tower.
c.In the design of insulator string.
d.Finding the distance between towers.
Ans: a
29.Hot template curves are plots of
a. temperature and humidity.
b. conductor sag and span length .
c.conductor weight and sag.
Ans: b
30. The effect of wind pressure is more predominant on
a. insulator.
b.transmission lines.
c.supporting towers.
Ans: c
31.Galloping in transmission line conductors arises due to
a. Asymmetrical layer of ice formation.
b. Vortex phenomenon in light winds.
C.Heavy weight of the line conductors.
d. Adoption of horizontal conductors configuration.
Ans:a
32. The sag of the conductors of a transmission line is 2.5 metre when the Span is 250 metre .Now if the height of supporting tower is increased by 25% , the sag will
a. Reduced by 25% .
b. Increased by 95% .
c.Reduced by 12.5% .
d.Remain unchanged.
Ans: d
33.Stranded conductors usually have a central wire around which there are successive layers of 6 ,12, 18 ,24 wires.For n layers ,the total number of individual wires is
a.3n(n+1) b. 2n(n+1) c.3n(n+1)+1 d.2n(n+1) +1
Ans: c
34.The diameter of each strand is d then the diameter of n layer stranded conductor will be
a. (2n+1)d. b. 3(n+1)d. c.(2n-1)d. d.3(n-1)d
Ans: a
35.Strain type insulators are used
a. At dead end
b. At intermideate anchor towers
c.On straight runs
d. a. and b.
Ans:d
36.Wavy structure of pin insulators increases its
a. Mechanical strength.
b. Puncture strength.
c.Flash over strength.
d. Thermal strength.
Ans:c
37.The voltage rating of a multiple shell pin type insulator unit cannot be increased beyond a limiting value by increasing the number of shells because,
a. The internal voltage distribution between shells becomes unequal.
b. The leakage path resistance starts diminishing .
c.The disruptive critical voltage for the material of the insulator is reached.
d. The puncture voltage of the material of the insulator is reached.
Ans:a
38. Post type insulators are generally used in lines operating
a.Avobe 100kv. b. below 33kv. c. at any voltage level ht or eht
Ans: c
39.In a string of insulators for 400 KV AC overhead transmission line lies in the range of
a. 32 to 33. b. 22 to 23 . c. 15 to 16 . d. 9 to 10
Ans:b.
Note:
2-3------33kv
5-6------66Kv
9-10-----132Kv
15-16------220kv
40. The non uniform distribution of voltage across the units in a string of suspension type insulator is due to
a . Unequal self capacitance of the units .
b.non-uniform distance of separation of the units from the tower body.
c. the existence of stray capacitance between the metallic junctions of the units and the tour body
d. non uniform distance between the cross arms and the units
Ans: c
41. The string efficiency of a string of suspension insulators is dependent on
a. size of the insulators. b. number of disc in the string. c. size of Tower
Ans: bb.
42. If the frequency of transmission system is changed from 50 Hz to 100 Hz,the string efficiency .
a. will increases. b. will decreases .
c. remain unchanged .
d. parameters may increases or decreases depending on the line parameters
Ans: c
43. The string efficiency of a High Voltage line is around
a. Hundred percent B. the 80%. c. 40. d.10%
44. The ratio of puncture voltage to the flash over voltage of a line insulator is
a. equal to 1
b.lower than one.
C.much greater than 1
Ans: c
45. The insulators may fail due to
a.flash over. b.short circuit.Deposition of dust. d. any of the avobe
Ans: d
46. The purpose of Guard ring in transmission lines is to
a.reduce the earth capacitance of the lowest unit
b. increased the earth capacitance of the lowest unit
c. reduce the transmission line losses d.increase the voltage distribution across the disc
Ans: a
47. Corona is
a. partial breakdown of Air .
b.complete breakdown of air
c. sparking between lines.
d.increase of resistance in line
Ans: b
48.Which of the following statements is true regarding Corona
a. Corona takes place at a voltage lower than breakdown voltage
b. takes place at a voltage higher than breakdown voltage.
c. Corona is a current phenomenon.
d. Corona increases the transmission line efficiency.
Ans: a
49.Ozone effect can be detected by
a.presence of ozone detected by odour.
b. hissing sound. c. faint luminous glow of bluish colour. d. all of the above
Ans: d
50. Corona loss increases with
a.decrease in conductor size and increase in supply frequency
b. increased in both conductor size and supply frequency
c. decrease in both conductor size and supply frequency
d. increase in conductor size and decrease in supply frequency
Ans: a
See the loss fomula of corona.
51.The good effect of Corona on overhead lines is to
a. increase the line carrying capacity due to conducting ionized air envelope around the conductor
b. Increase the power factor due to Corona loss.
c. reduces the radio interference from the conductor
d. Reduce the steepness of surge fronts.
Ans : d
52.Corona loss can be reduced by the use of hollow conductor because
a. the current density is reduced
b. the Eddy current in the conductor is eliminated.
c. for a given cross-section, the radius of the conductor is increased.
d. of better ventilation in the conductor
Ans: c
53. Bundled conductors reduce
a.surface electric stress of conductor
b. increases the line reactance.
c. decreases the line capacitance
Ans: a
54.The charging current transmission line increases due to corona effect because Corona increases
a.line current. b. effective line voltage. c.power loss in lines. d. the effective conductor diameter
Ans: d
55. The only advantage of Corona is that it
a. produces a pulsating Luminous glow.
b. makes line current sinusoidal.
c. works as a safety valve for surgesd.
d. the ozone gas is produced
Ans: c
56.What is the approximate breakdown strength of atmospheric air at N.T.P?
a. 0.3kv/cm b. 1.0 kv/cm. c. 3kv/cm. d. 30kv/cm
Ans: d
57.Skin effect in transmission line is due to a.supply frequency b. self inductance of conductor. c. high sensitivity of material in the centre. D both a. And b
Ans: d
58: when an alternating current flows through a conductor
a. Entire current passes through the core of the conductor
b. portion of conductor near the surface carries more current in comparison to the core.
C.current remains uniformly distributed over the cross section of the conductor
d. portion of conductor near the surface carries lesscurrent in comparison to the Core.
Ans: b
59. Iincreasing the frequency of transmission line will
a. increase shunt reactance. b. decrease line resistance. c. increase line resistance. d. decrease series resistance
Ans: c
60.Skin effect exist in
a. cable carrying DC current.
b.d c transmission line only. c. a c transmission line only. d. DC as well as AC transmission line.
Ans: c
True false question
61. single phase AC power pulsates around the average value at the supply frequency. Ans: False
62. the best method is to employ DC system for generation and distribution and ac system for transmission. Ans: False
63. Overhead system is more safer than underground system. Ans: False
64. The voltage drop in underground system is very low as compared to to that in overhead system. Ans: True
65. With the increase in voltage of transmission the insulation needed between the conductors and earthed tower increases. Ans: True
66. Economical cross section of conductor can be determined by Ferranti effect. Ans: False
67. Guy wire generally make an angle of 45 degree to 60 degree with the surface of the earth. Ans: True.
68. Increase in temperature in overhead transmission line causes decrease in stress but increase in length. Ans: True
69. Sag is directly proportional to the square of the span. Ans: True
70.Top most conductor in HV transmission line is earth conductor. Ans: True
..............
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